Method of preparing sodium sulfate and compounds of lead.



utilized assu'ch, or may serve for the preparation of UNITED STATES ALEXANDER s. RAMAQE,

Original application filed May 15. 19070 To all whom it may concern: Be' it known that I, ALEXANDER S. RAMAGE, a citizen of-the'United States, residing at Detroit, in the county of Wayne and State of Michigan, have inventedtc'ertain new and useful Improvements in Methods of Preparing Sodium Sulfate and Compounds of Lead,

of which the following is a specification.

This invention relates to the utilization oflead sulfate, and; lparticularly the material containing lead sulfate and sulfuric acid which constitutes a byprodnet of the manufacture of sulfuric acid by the chamber process.

According to the invention the lead sulfate is converted into a basic carbonate under conditions which yield a solution from which pure sodium sulfate may be recovered. The basic carbonate of lead may be pure solutions for the manufacture of chrome pigments as described in my co-p'ending pplication, Ser. No. 373,715, filed May-15, 1907, of which the present application is a division. The acid constituents of the byproduct above mentioned and hereinafter referred to as chamber sulfate are utilizedin the process.

The invention will be described by rcferenceto the treatment bf such chamber sulfate, but it will be understood that it is applicable to the treatment of lead sulfate from other sources by supplying the necessary sulfuric acid.

fMy preferred procedure is substantially as follows:" A suitable quantity, as chamber sulfate,

for instance one'ton, of the containing as a rule s me ten per cent of free sulfuric acid, is agitated with water in a suitable tank provided with a brass stirring device and suitable heating means, nd is then allowed to settle and the clcar liquid decanted, this treatment being preferably repeated several times until the free old is completely removed. This t catrnent applies only to the initial batch of sulfate as will appear hereafter. The washed sulfate is then treated with a solution containing for each pound of metallic lead contained in the sulfat at least 0.26 pounds of sodium hydroxid and 0171') pounds of sodium carbonate, and the whole is boiled for about iii'tccn minutes. The sulfate of lead is completely con verted into basic lead carbonate having the approximate formula PbCO 2PbH O while the solutioncontains sodium sulfate, sodium carbonate and snne lead. The contents of the tank are then filtcrcd, and the basic carbonate washed with water until freed from sulfates. The alkaline filtrate is run into anothetank containing about one ton of chamber sulfate which has not been washed to free it from acid. This free sulfuric acid reacts with the sodium carbonate of the solution rendering the solution acid. In case the chamber sulfate does not contain sufiicient Specification of Letters Patent.

Serial No. 373.715- Dividod and this application filed September 21. 1907.

Serial No. 393.985.

iiernu'r OFFICE.

OF DETROIT, MICHIGAN.

Patented Nov. 12, 1907.

free acid to render the solution distinctly acid to litmus paper, further portions of chamber sulfate or of sulfuric acid are added until this condition is attained. The lead held in solution will then' be completely precipitated, as lead sulfate is substantially insoluble in a strong saline solution having an acid reaction. The solution, containing only sodium sulfate, .together with impurities and a trace of sulfuric acid is then separated from the lead sulfate, and treated as hereinafter stantially neutral, is then treated without further washing with a solution of sodium hydroxid and carbonate under conditions substantially as above debasic carbonate. The alkaline solution derived from this second batch of basic. carbonate is available for neutralizing further portions of the chamber sulfate.

The slightly acid solution above described, consisting chiefly of sodium sulfate is treated in unsuitable tank with a small amount of ehlorid of lime to oxidize the impurities, is then neutralized with sodium carbonate, boiled, filtered, and then cooled to about degrees F. Sodium sulfate'crystallizes 'out on standing, and may be separated by meansof a hydro-extractor and dried in theusual way to produce anhydrous sodium sulfate.

I claim:

with an alkali metal carbonate and hydroxid to produce basic lead carbonate, acidifying the resulting solution by sulfate. 2. The method which consists in' reacting on lend sulfate with an alkali metal carbonate and hydroxid to produce basic lead carbonate, acidifying the resulting solution by sulfuric acid to eliminate the lead, neutralizing and purifying the solution, and separating sodium sulfate by refrigeration.

The method which consists in reacting on lead sulfate basic lead carbonate, bringing the resulting solution'into contact with chamber sulfate, thereby acidifying said solution and eliminating lend therefrom and obstructing acid from said chamber sulfate. neutralizing andpuriiying the solution, and separating sodium sulfate by refrigeration.

4. The method which consists in reacting on lead sulfate .with an alkali metal carbonate and hydroxid to produce busic lead carbonate. bringing the resultingsoiution into contact with chamber sulfate, thereby acidifying said solutlon and eliminating lend therefrom and obstructing acid from snid chamber sulfate, converting said sulfate into basic carbonate of lead. neutralizing and purifying the solution, and separating sodium sulfate h'y refrigeration.

in testimony whereof, I ufiix my signature in presence oftwo witnesses.

ALEXANDER s. amnion.

Witnesses WALLAcn N. OSBURN, HERMAN Annnsou.

scribed for the production of further quantities of the 1. The method which consists in reacting on lead sulfatesulfuric acid to eliminate the lead, and separating sodiumwith an alkali metal carbonate and hydroxid to produce described. The sulfate of lead in the tank, being sub- 

